For the vast majority of human history, agriculture can be described as "organic"; only during the 20th century was a large supply of new synthetic chemicals introduced to the food supply. The organic farming movement arose in the 1940s in response to the industrialization of agriculture known as the Green Revolution.The weight of the available scientific evidence has not shown a significant difference between organic and more conventionally grown food in terms of safety, nutritional value, or taste.

Organic food production is a heavily regulated industry, distinct from private gardening. Currently, the European Union, the United States, Canada, Japan and many other countries require producers to obtain special certification in order to market food as "organic" within their borders. In the context of these regulations, "organic food" is food made in a way that complies with organic standards set by national governments and international organizations. In the United States, organic production is a system that is managed in accordance with the Organic Foods Production Act (OFPA) of 1990 and regulations in Title 7, Part 205 of the Code of Federal Regulations to respond to site-specific conditions by integrating cultural, biological, and mechanical practices that foster cycling of resources, promote ecological balance, and conserve biodiversity. If livestock are involved, the livestock must be reared with regular access to pasture and without the routine use of antibiotics or growth hormones. In most countries, organic produce may not be genetically modified. It has been suggested that the application of nanotechnology to food and agriculture is a further technology that needs to be excluded from certified organic food. The Soil Association (UK) has been the first organic certifier to implement a nano-exclusion.

Meaning and origin of the term

In 1939, Lord Northbourne coined the term organic farming in his book Look to the Land (1940), out of his conception of "the farm as organism," to describe a holistic, ecologically-balanced approach to farming—in contrast to what he called chemical farming, which relied on "imported fertility" and "cannot be self-sufficient nor an organic whole." This is different from the scientific use of the term "organic," to refer to a class of molecules that contain carbon, especially those involved in the chemistry of life.

Identifying organic food

Processed organic food usually contains only organic ingredients. If non-organic ingredients are present, at least a certain percentage of the food's total plant and animal ingredients must be organic (95% in the United States, Canada, and Australia) and any non-organically produced ingredients are subject to various agricultural requirements. Foods claiming to be organic must be free of artificial food additives, and are often processed with fewer artificial methods, materials and conditions, such as chemical ripening, food irradiation, and genetically modified ingredients. Pesticides are allowed so long as they are not synthetic.

Early consumers interested in organic food would look for non-chemically treated, non-use of unapproved pesticides, fresh or minimally processed food. They mostly had to buy directly from growers: "Know your farmer, know your food" was the motto. Personal definitions of what constituted "organic" were developed through firsthand experience: by talking to farmers, seeing farm conditions, and farming activities. Small farms grew vegetables (and raised livestock) using organic farming practices, with or without certification, and the individual consumer monitored. As demand for organic foods continued to increase, high volume sales through mass outlets such as supermarkets rapidly replaced the direct farmer connection. Today there is no limit to organic farm sizes and many large corporate farms currently have an organic division. However, for supermarket consumers, food production is not easily observable, and product labeling, like "certified organic", is relied on. Government regulations and third-party inspectors are looked to for assurance.

The USDA carries out routine inspections of farms that produce USDA Organic labeled foods. Of the 30 third party inspectors 15 of them have been placed under probation after an audit. On April 20, 2010, the Department of Agriculture said that it would begin enforcing rules requiring the spot testing of organically grown foods for traces of pesticides, after an auditor exposed major gaps in federal oversight of the organic food industry.

Several surveys and studies have attempted to examine and compare conventional and organic systems of farming. The general consensus across these surveys is that organic farming is less damaging for numerous reasons.

According to reports released by the nonprofitFood & Water Watch 11/2013, the GM/biotech industry has spent $547 million on lobbying efforts and campaign contributions, in Washington, to prevent the truth from coming out about the environmental impact of GM crops. Studies of GM crops in developing countries and throughout the world have demonstrated that GM seeds need more water, fertilizer and pesticides than conventional crops. In areas with cycles of drought – GM seeds are creating a crisis of epic proportions.GM corn is pushing the world’s water supply to the brink. Another lie from the biotech industry – GM corn doesn’t need less water than other corn. GM corn is not drought resistant. The agricultural giant, Monsanto, would like us to believe that their corn saves water. Corn is an extremely thirsty crop that requires much more water than wheat. In fact, it requires over 20 inches of irrigation water in many places where is grows.One of the reasons corn is depleting our underground water supply is because it replaces other water conserving plants. These are non-native species being planted in areas where they are draining the underground water reservoirs. Experts suggest this could lead to another ‘dust bowl’ era in the United States.Nearly 70 percent of the groundwater is stored in parts of the United States’ High Plains aquifer, that stretches from South Dakota to Texas. It supplies 30 percent of the nation’s irrigated groundwater and could be used up within 50 years.

Yield

One study found a 20% smaller yield from organic farms using 50% less fertilizer and 97% less pesticide. Studies comparing yields have had mixed results. Supporters claim that organically managed soil has a higher quality and higher water retention. This may help increase yields for organic farms in drought years.

One study from the Danish Environmental Protection Agency found that, area-for-area, organic farms of potatoes, sugar beet and seed grass produce as little as half the output of conventional farming. Michael Pollan, author of The Omnivore's Dilemma, responds to this by pointing out that the average yield of world agriculture is substantially lower than modern sustainable farming yields. Bringing average world yields up to modern organic levels could increase the world's food supply by 50%.

A 2007 study compiling research from 293 different comparisons into a single study to assess the overall efficiency of the two agricultural systems has concluded that, organic methods could produce enough food on a global per capita basis to sustain the current human population, and potentially an even larger population, without increasing the agricultural land base. (from the abstract)

The researchers also found that while in developed countries, organic systems on average produce 92% of the yield produced by conventional agriculture, organic systems produce 80% more than conventional farms in developing countries, because the materials needed for organic farming are more accessible than synthetic farming materials to farmers in some poor countries. On the other hand, communities that lack sufficient manure to replenish soils would struggle with organic farming, and the soil would degrade rapidly.

Energy efficiency

A study of the sustainability of apple production systems showed that in comparing a conventional farming system to an organic method of farming, the organic system is more energy efficient. A more comprehensive study compared efficiency of agriculture for products such as grain, roughage crops, and animal husbandry. While the study did not investigate specific additional requirements of arable land or numbers of farm laborers to produce total yields for organic farming vs. conventional farming, leaving open the question of overall capacity of organic farming to meet current and future agricultural needs, it concluded that organic farming had a higher yield per unit of energy over multiple crops and for livestock. However, conventional farming had higher total yield. Conversely, another study noted that organic wheat and corn production was more energy efficient than conventional methods while organic apple and potato production was less energy efficient than conventional methods. A long-term study, spanning two decades, noted that crop yields were 20% lower in organic systems while fertilizer plus energy input was 34% to 53% lower. However, pesticide input was reduced by 97% in organic farm systems.

Consumer Safety

There is widespread belief that organic food is significantly safer for consumption than food grown conventionally, based mainly on anecdotal evidence and testimonials rather than scientific evidence, which has fueled increased demand for organic food despite higher prices. Reviews of the available body of scientific literature comparing the safety of organic to conventional foods have found neither to be significantly more, safe than the other. Firm conclusions about the relative safety of organic foods has been hampered by the difficulty in proper study design and relatively small number of studies directly comparing organic food to conventional food.

Claims of improved safety of organic food, has largely focused on pesticide residues. While studies have shown organically grown fruits and vegetables have significantly lower pesticide residue levels, the significance of this finding on actual health risk reduction is debatable as both conventional foods and organic foods generally have pesticide levels well below government established guidelines for what is considered safe. This view has been echoed by the U.S. Department of Agriculture and the UK Food Standards Agency. Claims of increased risk related to pesticide residue and rates of infertility or lower sperm counts have not been supported by the evidence in the medical literature. Reviews have noted that the risks from microbiological sources or natural toxins are likely to be much more significant than short term or chronic risks from pesticide residues.

Some focus has been placed on the amount of nitrogen content in certain vegetables, especially green leafy vegetables and tubers when grown organically as compared to conventionally. While these vegetables, when grown organically, have been found to have lower nitrogen content, there is no consensus as to whether consumption of lower levels of nitrogen translates to improved health risk. When evaluating environmental toxins such as heavy metals, the USDA noted that organically raised chicken may have lower arsenic levels, while a literature review found no significant evidence that levels of arsenic, cadmium or other heavy metals differed significantly between organic and conventional food products. In looking at possible increased risk to safety from organic food consumption, reviews have found that although there are theoretical increased risk from microbiological contamination due to increased manure use as fertilizer from organisms like E. coliO157:H7 during organic produce production, there does not exist sufficient evidence of actual incidence of outbreaks that can be clearly tied to organic food production to draw any firm conclusions. Other possible sources of increased safety risk from organic food consumption like use of biological pesticides or the theoretical risk from mycotoxins from fungi grown on products due to the lack of effective organic compliant fungicides have likewise not been confirmed by rigorous studies in the scientific literature.

Nutritional value and taste

According to the UK's Food Standards Agency, "Consumers may choose to buy organic fruit, vegetables and meat because they believe them to be more nutritious than other food. However, the balance of current scientific evidence does not support this view." A 12-month systematic review commissioned by the FSA in 2009 and conducted at the London School of Hygiene & Tropical Medicine based on 50 years' worth of collected evidence concluded that "there is no good evidence that consumption of organic food is beneficial to health in relation to nutrient content." Other studies have found no proof that organic food offers greater nutritional values, more consumer safety or any distinguishable difference in taste. A recent review of nutrition claims showed that organic food proponents are unreliable information sources which harm consumers, and that consumers are wasting their money if they buy organic food believing that that it contains better nutrients.

Although it is commonly claimed that organically grown food tastes better than conventionally grown food, reviews of the literature that looked at the sensory qualities of the two have not found convincing evidence that there is any significant differences.

Economics

Demand for organic foods is primarily concerned for personal health and for the environment. Organic products typically cost 10 to 40% more than similar conventionally produced products. According to the USDA, Americans, on average, spent $1,347 on groceries in 2004, thus switching entirely to organics would raise their cost of groceries by about $135 to $539 per year ($11 to $45 per month) assuming that prices remained stable with increased demand. Processed organic foods vary in price when compared to their conventional counterparts.

While organic food accounts for 1–2% of total food sales worldwide, the organic food market is growing rapidly, far ahead of the rest of the food industry, in both developed and developing nations.